Area Forecast Discussion
Issued by NWS Duluth, MN
Issued by NWS Duluth, MN
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208 FXUS63 KDLH 301747 AFDDLH Area Forecast Discussion National Weather Service Duluth MN 1247 PM CDT Tue Apr 30 2024 .KEY MESSAGES... - Fog creating areas of low visibility around 1/2 mile very early this morning lifts from mid to late morning today. - Another quickly moving system will create 1/4 to 1 inch of rainfall across the Northland beginning this evening in north- central and northeast Minnesota and exiting the region early Wednesday morning. Thunder and lightning is possible (30% chance in east-central MN and northwest WI), but severe storms are not expected. - A second system is likely (70% chance) to bring a late week round of rainfall from Thursday morning into Friday, with continued off-and-on rain and thunderstorm chances into the weekend and early next week. && .DISCUSSION... Issued at 357 AM CDT Tue Apr 30 2024 Infrared satellite imagery shows the low pressure that brought the Northland a wet half of Sunday and foggy/drizzle Sunday is now located in far northwest Ontario early this morning. Trailing rain showers have all but moved out of the Arrowhead over the last few hours, with only drizzle, fog and mist ongoing across the region under very low sky decks behind the low pressure. These low clouds stick around through this morning, but gradually scour out into this afternoon as drier air aloft is already working overhead from mid-level ridging moving from the Northern Plains into the Upper Midwest. That mid-level ridge is very short-lived though as the next low pressure lifts northward from the Central Plains into the Upper Midwest by late this afternoon. The incoming moisture plume on southerly low to mid-level flow increases sky cover again from southwest to northeast late this afternoon and into the evening ahead of the next band of rainfall. The low tracking from south-central Minnesota to northwest Wisconsin tonight favors the best chances for widerspread thunderstorm activity south of the forecast area. Mid-level lapse rates around 7 C/km and available MUCAPE up to 50 J/kg indicate limited thunder/lightning potential (30% chance) though for east-central Minnesota to northwest Wisconsin late this evening and early overnight. Model sounding data shows precipitable water values of 0.9-1.1 inches in the column (about the 90-95th percentile for today) in east-central MN and across northwest Wisconsin favoring a 20% chance of a maximum location of 1-1.25 inch rainfall total by early Wednesday morning. The rest of the Northland is expected to see 1/4 to 3/4 of an inch of rainfall as the vort max within the quick- moving low pressure exits the forecast area by Wednesday mid- morning. For locations at the Head of the Lake and along lakeshores, increasing easterly winds are likely (80% chance) too. Wind gusts of 25 to 30 mph (60% chance) are expected at this time in the mid evening hours to early overnight time period as the low pressure center crosses through northwest Wisconsin. Deep mid-level troughing that has been in place over the northern Rockies and Pacific northwest moves towards the middle of the Continental US by mid-week. Sunny skies setup under a period of subsidence by Wednesday late afternoon and evening, so these late afternoon dewpoint temperatures were decreased towards the 10th percentile guidance to create around a 5-10% drop in forecast relative humidity for that day over base guidance. Recent moderate to heavy rainfall should help to minimize fire weather concerns though even with increasing westerly winds starting late Wednesday morning. As that mean troughing enters the Northern Plains into Wednesday night, a southerly low-level jet increases moisture south to northward Thursday daytime. Thursday late morning into the night is the second chance for widespread rainfall chances this week. Another few tenths of an inch of rain may (40 to 60% chance) fall in this late week system before off-and-on rain chances last into this weekend and early next week. Near-seasonal temperature prevail in this active and somewhat wet period. && .AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/... Issued at 1247 PM CDT Tue Apr 30 2024 Stubborn stratocumulus clouds with a few embedded light showers will be slow to diminish this afternoon, but there is still potential for there to be a period of VFR ceilings for a few hours later this afternoon where clouds have not broken yet. As we go into this evening, rain is expected to quickly spread into the region from southwest to northeast. Expect ceilings to fall pretty rapidly to MVFR/IFR and visibility to fall mainly to MVFR as well and remain so for much of the night. Thunder is not expected at most terminals, but HYR will have the best chance (20-30%) at seeing some. After the rain ends from southwest to northeast Wednesday morning, lingering low-level stratus are expected to stick around through much of the morning. Winds will gradually shift to east/northeasterly this evening ahead of the rain and become breezy at DLH with gusts up to 20-30 kt. Winds are expected to shift fairly abruptly to westerly Wednesday morning after rain moves northeast. && .MARINE... Issued at 1001 AM CDT Tue Apr 30 2024 Some headline adjustments have been made along the South Shore and Outer Apostle Islands to extend Small Craft Advisories into mid-day Wednesday as latest models suggest that gusty winds will persist there with northeast flow. No other changes at this time from the previous update. For the open water discussion, refer to the NWS Marquette Area Forecast Discussion at weather.gov/mqt. && .DLH WATCHES/WARNINGS/ADVISORIES... MN...None. WI...None. MARINE...Small Craft Advisory from 10 PM this evening to 10 AM CDT Wednesday for LSZ140>142. Small Craft Advisory from 7 PM this evening to 10 AM CDT Wednesday for LSZ143. Small Craft Advisory from 7 PM this evening to 4 AM CDT Wednesday for LSZ144-145. Small Craft Advisory from 10 PM this evening to 4 PM CDT Wednesday for LSZ146-147-150. Small Craft Advisory from 10 PM this evening to 4 AM CDT Wednesday for LSZ148. && $$ DISCUSSION...NLy AVIATION...JDS MARINE...JDS